Electrolysis switch



15 7 POWER souac: 16 l 1 Z0 CABLE SHEATH March 5, 1946. Q Q BAGWELL 2,395,833

Y ELECTROLYSIS SWITCH Filed Jan. 9, 1943 INVENTOR.

OMAR C. BAGWELL BY fanny Maw Patented Mar. 5, 1946 UNITED STATES PATENT orrlcs Omar C. Bagwell, New York, N. Y., assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application January 9, 1943, Serial No. 471,855

3 Claims.

This invention relates to an electrolysis switch and more particularly to a solenoid and rectifier circuit for protecting underground cable sheaths, water pipes and the like from electrolysis.

An object of the invention is the provision of a simple and efiicient electrolysis switch which may be produced at low cost and which will operate with a minimum of attention.

As is known, stray currents from street car tracks and electric railway tracks sometimes produce earth currents which fiow along buried pipes or cable sheaths and which leave these pipes or cable sheaths at some point nearer the power house causing a gradual erosion of the pipe or cable sheath in the area where the current leaves due to electrolysis.

To overcome this difilculty it has been common practice in the past to make a return connection from some suitable point on the cable sheath or water pipe to the power supply circuit from which the earth currents originate. This connection is of low resistance and conducts the earth currents directly from the underground pipe so that there is no difierence in potential between the pipe and the earth in the area adjacent to where the connection is made and therefore no electrolysis occurs.

A disadvantage of the arrangement just described is that in the case of a shutdown of the power supply circuit from which the earth currents originate, or in the case of a considerable variation in the amount of earth current picked up by the cable sheath, the conditions may become such that the conductor connecting the cable sheath with the power supply will itself become a hazard since due to its low resistance it may pick up earth currents from other power circuits flowing in a direction the reverse from normal and feed such currents to the cable sheath which will result in electrolysis in the area where these currents leave the cable sheath. The present invention seeks to eliminate these disadvantages by means of a novel circuit arrangement now about to be described with the aid of the accompanying drawing of which the single figure shows a schematic circuit for an electrolysis switch according to the present invention.

Referring to the drawing? Reference character l0 indicates a. solenoid having a plunger ll provided with a contact member l2 which when the solenoid is energized bridges contacts I3 and I4 connected respectively to opposite terminals of rectifier l5.

One terminal of the solenoid is connected to a terminal l6 of the rectifier while the opposite terminal or the solenoid is connected via a !use 18 to a source of current It! which maybe a conductor of suitable polarity of the power mains. Terminal 20 of the rectifier is connected at 2| to the cable sheath or water pipe which is to be protected from electrolysis.

The electrical conditions causing electrolysis vary considerably with each locality, but generally they are of low voltage and quite high amperage. Under normal operating conditions the electrical characteristics of the circuit are such that solenoid I0 is not energized sufllciently to close its contacts and point I 9 of the circuit is connected to point 2| via the winding of solenoid l0 and rectifier IS. The rectifier is used merely as a valve since practically all street car and railway systems operate on direct current. If the current in the solenoid windings rises sufilciently, the contacts close, short-circuiting and thus protecting the rectifier elements from an overload and at the same time reducing the resistance of the circuit by eliminating that of the rectifier unit. If the current subsequently decreases to a normal value, the solenoid contacts open and the rectifier is again connected in circuit.

The cable sheath is protected by the rectifier unit from any stray currents flowing in the reverse direction from normal which might be picked up by the conductor. Any of a number of conditions might create this situation. For example, assume that any given cable sheath or the like is protected from electrolysis by a simple underground conductor connecting the cable sheath and some suitable point in the street railway circuit from which the stray currents originate, the conductor serving as a low resistance return for the stray currents. Assuming also that the protection afforded is adequate under normal conditions while the railway circuit is energized, then, if for any reason current is cut off from the particular tracks from which the leakage occurred, no current from this source will flow in the cable sheath, but the earth currents formerly coming from the tracks may have had the efiect of balancing out earth currents of opposite polarity from other sources, for example other power houses or other tracks, and the conductor also might serve as a means for picking up such other stray currents of opposite polarity which if permitted to flow from the conductor into the cable sheath might cause electrolysis between the cable sheath and ground. The rectifier arrangement shown in the present invention prevents currents having a polarity which is opposite that of the normal current, from flowing from the circuit I9-2l into the cable sheath.

If the polarity of the current be reversed in the circuit I9--2i from that shown in the drawing, the value of the current during part of the reversal cycle would be zero and the windings of solenoid l would become deenergized and contacts l3 and H would open, thereby opening the circuit by-passing rectifier IS. The solenoid cannot reoperate because rectifier I5 is in series with the solenoid windings and the rectifier is so poled that no current now flows therethrough.

What is claimed is:

1. In an arrangement for protecting an underground conducting surface from electrolysis, a circuit connected to said surface to form a path for conducting away from said surface stray currents picked up thereby, and a rectifier in said circuit for preventing the flow of current from said circuit to said surface.

2. In an arrangement for protecting an underground conducting surface from electrolysis due to the effect oi stray electric currents picked up by the conducting surface flowing therefrom into the earth, a circuit connected to said surface for conducting said stray electric currents therefrom, means comprising a rectifier in said circuit for preventing stray currents picked up by said circuit from flowing back to said surface, and means comprising a magnetic device responsive to stronger-than-normal currents in said circuit for protecting said rectifier from injury from said currents.

3. An arrangement according to claim 2 in which said magnetic device comprises a solenoid connected in series in said circuit, a plunger for said solenoid, contact means disposed so as to be closed by said plunger when said solenoid ls sufflciently energized, said contact means being connected to opposite terminals of said rectifier, whereby said rectifier is short circuited when said contact means are closed.

OMAR C. BAGWELL. 

